Drilling holes in the gel coat

[hunkydory]

We ordered a companionway cover and now need to install some snaps into the fiberglass. I plan on pre drilling and using 3m 5200 to seal them in the hole. I'm just a little nervous to drill into the gel coat. Does it crack easily? Are there any tricks to prevent cracking?

Thanks,
Robin

 

[Drew13440]

It may be a wives tale, but I put masking tape down, mark the spot on that and have never had problems. The screw snaps you'll be using also likely have a lip that will cover any chipping.

Drilling a hole in your boat is tough, but it'll get easier every time!

 

[Rick Webb]

Run the Drill Backwards first Through the Gelcoat

The masking tape won't hurt. The first couple are the most dificult but you gain confidence with each one. I looked at the spot for an hour before I drilled the first hole in my boat.

 

[Bob 04 H260]

Robin, most people don't recommend 5200 in most cases, there is a good thread about this on another forum, checkout post #19 in the thread in the link below.

I find it is best to drill into the gel coat with with the tip of a much larger drill bit. This will leave a conical hole in the gel coat, then drill through the fiberglass with a smaller drill bit. The conical hole in the gel coat will help to provide a seal and later on it will stop star-shaped cracks from forming around the hole you have drilled. I have had good success using butyl as a sealant. The butyl does a good job of sealing up a joint, it is easy to control and clean up, and always easy to take it apart. If you do hit any area with wood coring you will have to drill the hole oversize, fill the hole with epoxy and redrill in the smaller size required for your fastener.

good luck, Bob

5200 link here,
http://www.sailnet.com/forums/gear-maintenance/52545-3m-5200-a-2.html

also a very good post (or is it the bible) on using butyl here,
http://www.sailnet.com/forums/gear-maintenance/63554-bedding-deck-hardware-butyl-tape.html

 

[cephius (Dave)]

The gel coat does tend to chip around the hole, even under the tape. I like to use a large, sharp bit to just cut the surface. About a 5/16". I use just the tip to make a 1/4" wide cut. It gives me a counter sink to drill in and keeps the actual bit from catching and chipping. This goes faster if you have two drills.

Even without this precaution, the chipped area never exceeds the size of the snaps.

Opps, looks like Bob beat me to this tip.

 

[Rick Macdonald]

When I installed my cover, it took an hour to drill the first hole and a few seconds to drill the last. An excellent tip I got on this forum was to drill the hole wth the drill in reverse. This greatly helps avoid chipping off large flakes. I don't recall if I used 4200 or 5200. It was about 7 years ago. Oh, another tip I got here was to install the socket part of the snap on the canvas first, then press or tap on it against the deck to mark the surface location for drilling. My sunbrella canvas has shrunk a bit over the years, making it tighter than it used to be.

 

[hunkydory]

Great info, thanks!